SCR catalyst and its preparation method and applications

A method for preparing an SCR catalyst, the method comprising:

• (1) placing a first aqueous solution containing a titanium oxide and a tungstate in an electric field, adjusting the pH value of the first aqueous solution, and adjusting a current direction of the electric field to obtain a first mixture;
• (2) adding dropwise a second aqueous solution containing a soluble salt of one or more active components, a copper-organic polyamine complex and a dispersant to the first mixture, and adjusting the current direction to obtain a second mixture, wherein the one or more active components are selected from a group consisting of Ce, Zr, Cu, Fe, Pr and Sc;
• and
• (3) processing the second mixture to obtain the SCR catalyst, wherein processing the second mixture comprises one or more of aging, filtering, washing, drying, or calcining;
• wherein step (1) comprises:
• adjusting the current direction to a direction A when the pH value of the first aqueous solution is <5;
• adjusting the current direction to a direction B when the pH value of the first aqueous solution ranges from 5-9;
• and
• adjusting the current direction to the direction A when the pH value of the first aqueous solution ranges from 9-10,
• wherein the direction A and the direction B are opposite
• wherein in step (2):
• during the dropwise addition, the direction of current is adjusted to the direction A;
• and
• after the dropwise addition, the direction of current is adjusted to the direction B.